We can say that static URLs have physical existence and it display same information for all users. The page really exists on the server. Basically, HTML files are known as static URL.

Benefits of Static URLs:

The URLs are known as cache and search engines friendly.

These get higher ranking in search engines.

These are Ideal for promotion in search engines.
Disadvantages of Static URLs:

If the site is very large then it is very difficult to maintain static URLs.

Portals, big sites or e-commerce sites are not possible with static URLs.

Dynamic URLs:

These are not like static URLs. Dynamic URLs have not its own existence. It comes from server. .ASP, .PHP, .JSP, .ASPX etc. are the well known name of dynamic URLs.

Benefits of Dynamic URLs:

For portals or e-commerce sites these are the best.

You can easily maintain 1000 of URLs and updates them dynamically.

Disadvantage of Dynamic URLs:

Dynamic URLs sometimes are not cache friendly.

These are long and create query string URLs.

Dynamic and static URLs depend on your business requirements. If your business is big and it deals are related to customer oriented products then you need to develop a dynamic web pages or dynamic sites. Now, most of sites are on the dynamic scripts. Dynamic pages use Clint side script and server side script to browse a web page.

In the dynamic web pages contents, image, script, web design are separate on the server and when a user request an id then all the things come jointly on the browser.